1. Field of the Invention
This invention relates in general to submersible pump motors, and in particular to a bearing assembly that resists rotation and is located between rotor sections for supporting the shaft of the motor.
2. Description of the Prior Art
A submersible pump is a centrifugal pump having a submersible motor that rotates the shaft to drive the pump. The motors for high volume oil and water production may be from six to sixty feet in length and be rated at several hundred horsepower. Each motor has a stator secured within a tubular housing. A rotor secured to a shaft rotates within the stator.
Because of the long length, the rotor is made up of a number of rotor sections. Each rotor section comprises a large number of flat disks called laminations that are secured by copper rods. The rotor sections are spaced-apart from each other, and a bearing assembly is located between each section for maintaining the shaft in axial alignment. The rotor sections are keyed to the shaft for rotation, but are axially movable with respect to the shaft.
Each bearing assembly includes a sleeve keyed to the shaft for rotation. A journal, commonly called a bearing, has a bore with a periphery that frictionally engages the inner wall of the stator at operating temperatures to prevent the bearing from rotating and to support the shaft in alignment.
As the motor heats up to operating temperature, the bearing will expand slightly outward to more tightly grip the stator. Also, the rotor will likely grow longitudinally at a rate greater than the stator, causing the bearing to move longitudinally with respect to the stator. The bearing must be precisely dimensioned so that it does not engage the stator wall so tightly as to create excessive thrust loads on the bearing member. For accurate dimensioning, the bearing is normally constructed of a metal with an outer wall ground to a 0.0005 inch tolerance. While usually satisfactory, on occasion the bearing begins to spin with the shaft, causing heat and metal surfaces galling which ultimately leads to oil contamination and dielectric breakdown.
Proposals have been made to prevent the bearing from rotating. For example, in application Ser. No. 538,646, filed Oct. 3, 1983, Anti-Rotation Motor Bearing, David I. Del Serra, an annular elastomer for fitting about the bearing periphery is shown. The elastomer swells during operation to engage the stator inner wall to prevent rotation of the bearing. In U.S. Pat. No. 4,435,661, issued Mar. 6, 1984, Submersible Pump Motor Flexible Bearing, Raymond L. Witten, a resilient bearing is shown. The bearing has slots through the periphery to allow the bearing to be compressed during operation, to prevent rotation of the bearing. While these proposals have merit, other manners of solving the problem may be possible.